The production of saturated halohydrocarbons containing fluorine has recently been the subject of renewed interest as the products are identified as environmentally desirable compounds for use as solvents, blowing agents and refrigerants. The compounds have been produced using certain well-known catalytic processes for hydrogenolysis and/or hydrogenation of saturated or unsaturated compounds containing chlorine and fluorine.
Numerous catalysts for the hydrogenolysis or hydrogenation of halocarbons, including supported precious metal catalysts, are known. For example, British Patent Specification No. 1,578,933 discloses a process for the manufacture of CF.sub.3 CH.sub.2 F or CHF.sub.2 CHF.sub.2 by the hydrogenolysis of an appropriate haloethane over a hydrogenation catalyst. Palladium supported on carbon or alumina are specifically exemplified. In a typical example, CF.sub.3 CCl.sub.2 F is converted to a mixture of CF.sub.3 CHClF, CF.sub.3 CH.sub.2 F, and CF.sub.3 CH.sub.3. European Patent Publication No. 0324478 discloses a process for the preparation of 1,2-difluoroethane and 1,1,2-trifluoroethane which comprises reacting 1,2-dichloro-difluoroethylene or chlorotrifluoroethylene, respectively, with hydrogen in the gas phase in the presence of a hydrogenation catalyst comprising a transition metal; with palladium being preferred.
Supported metal catalysts such as palladium on carbon can exhibit poor selectivity. For example, in European Publication No. 0324478 it is seen that not only is hydrogen added to the olefinic bond, but chlorine atoms of the olefin are also replaced with hydrogen. It is clear that there is a need for more selective catalysts which allow control of reactions in order to produce not only fluorohydrocarbons (i.e., compounds containing only carbon, fluorine and hydrogen atoms) but also fluorohalohydrocarbons containing atoms of a halogen such as chlorine.
Precious metal catalysts such as palladium are expensive and can deactivate during the course of catalyzed reactions. Replacement and/or regeneration of such catalysts can thus add to the cost of the catalyzed reaction.
Iodine or hydrogen iodide have been used in conjunction with the reaction of certain perfluoro compounds. For example, U.S. Pat. No. 2,844,636 discloses a process for the manufacture of 1,1,2,3,4,4-hexafluorobutane by reacting perfluorocyclobutene with hydrogen, using elemental iodine as the catalyst. In this process not only is there hydrogen addition at the double bond, but also cleavage and hydrogenation at the --CF.sub.2 --CF.sub.2 --single bond to give the substituted normal butane. R. D. Chambers et al., J. Chem. Soc.(C), 1971, 61-67; disclose the reaction of perfluoroquinoline with an excess of hydrogen iodide to form 3,5,6,7,8-pentafluoroquinoline.